Gah. Is this really the right thread to say this? Whatever.
I don't like Defog. My strategies generally revolve around setting up dual screens, getting one of my sweepers in and then going 6-0. Defog removes that. Not to mention that as my team thrives on offensive pressure, and no users of it bar maybe Scizor fit as offense. (Scizor loses out its precious coverage anyhow if it does).
That's why Defog's 'risky', it can mess up your strategies as well. I've settled for using rapidspin Excadrill instead.
Hell, I haven't seen defog used more than a couple times in ou, and i've been playing gen 6 ou since the day XY was released. The only truly 'viable' defogger is Mandibuzz.